Published studies indicate that organophoshate insecticides can alter immunity in laboratory animals. The importance of such "immunotoxic" effects of these compounds on acquired immunity has not been adequately assessed, relative to the demonstrated biochemical indices of organophoshate exposure and toxicicity, i.e. tissue cholinesterase and carboxylesterase activity. Mice will be treated with Paration, Methylparathion, Fenitrothion, EPN, Malathion, Dichlovos, Diazinon or Abate at doses selected to produce a broad spectrum of esterase inhibition and toxicity. They will then be innoculated either with T-dependent or T-independent immunogens for assessment of humoral immunologic function. Similarly treated animals will be killed without innoculation for assessment of cell mediated immunologic function. The results will determine if the insecticide effects are nonspecific or limited to specific aspects of the acquired immune response. The results will also indicate the thresholds for organophoshpate effects on immunity for comparison with recognized biochemical effects.